Much time is spent in the Stage of Concrete Operations in developing palpable concepts.
To increase the height is to get more juice. Another hallmark of the Concrete Operations Stage is the ability of the child to categorize. The child is getting pretty good at handling groups of bonds. They can understand that if the height is increased, but the width is decreased there is no gain. So they are not fooled so easily.
This skill at comparing multiple bonds makes the child at the Concrete Operational stage ready to categorize the world.
The concreteness of the thought processes in this stage means that they are dealing mostly with palpable worldly objects. These are things that can be seen or felt in some way.
This would relate to the percept level of Kephart where adults are very busing helping the child to divide the world up into horses, shovels, houses, cars, etc. all with symbols attached.